Decompression device for internal combustion engines



DECOMPRESSION DEVICE FOR INTERNAL COMBUSTION ENGINES Filed March 15,1961 E. HATZ, JR

Oct. 9, 1962 2 Sheets-Sheet 2' United States Ratent G DECGMTPRESSIGNDEVIUE FGR INTERNAL QUMBIETIUN ENGINES Ernst Hatz, .Irz, Ruhstorf, nearPassau, Germany, assignor to Motorenr'ahrik Hatz, Gcseiiscirat't mitheschrankter Hat'tung, Rnhstorf, near Passau, Germany, a company ofGermany Filed Mar. 15, 1961, Ser. N 95,996 Claims priority, applicationGermany Oct. 6, 1960 11 Ctairns. (Cl. 123-482) This invention relates todecompression devices for assisting in the starting of valve controlledinternal combustion engines.

In this connection the invention is primarily applicable to an injectioncombustion, i.e. compression ignition, engine equipped with adecompression device of the kind comprising a decompression cam,arranged to act on a valve rocker actuated by an axially reciprocablepush rod, such cam being adapted to be rotated in a direction todiscontinue the decompression, either manually, or by automatic meansconsisting of a driving disc which is connected to the said cam and adriver co-operating therewith. In such an arrangement each upward strokeof the push rod so actuates the rocker as to open the valve, whereas ateach downward stroke of the said rod the valve is normally permitted toclose.

In a known decompression device of this character the driver is drivendirectly by teeth provided on a valve rocker, with the result that thecomplete decompression assembly must be arranged above this rocker.This, however, is a disadvantage because it considerably increases thespace required by the device and hence also the overall dimensions ofthe engine.

In another known form of decompression device, a leaf spring isconnected to the rocker and acts on a driving disc arranged above thelatter. It has been found, however, that this form of drive for thedecompression cam strains the spring and results in poor powertransmission characteristics.

The object of the present invention is to obviate the disadvantages ofthese known constructions and to provide a simple, compact andparticularly efficient improved form of decompression device of the kindherein referred to.

According to this invention, a decompression device of the kindspecified is characterized in that the driver is in the form of a memberwhich is provided on the axially reciprocable push rod, said memberbeing of circular form in transverse cross-section and having aperipheral edge which engages with and turns the driving disc duringvalve opening strokes of the push rod, the said member or a portionthereof moving idly aside radially in relation to the driving discduring valve closing strokes of the said rod.

In a preferred embodiment of the invention the driver is in the form ofa cup-shaped sleeve which surrounds the push rod and is resilientlybiased against a collar on this rod. Alternatively, however, the drivermay be in the form of a cup-shaped sleeve which surrounds the push rodand is firmly connected thereto, this sleeve being axially slitpartially along its length suchwise as to provide around the circularperiphery a plurality of resilient tongues each capable of engaging withthe driving disc.

In order that the invention may be more clearly understood and readilycarried into practical effect, specific constructional examples thereofwill now be described with reference to the accompanying drawing,wherein,

FIGURE 1 is a vertical cross sectional view of so much of an internalcombustion engine as is necessary to illustrate the application theretoof one form of the decompression device provided in accordance with theinvention,

FIGURES 2 and 3 show, in two different operative positions, part of thedevice illustrated in FIGURE 1,

FIGURE 4 depicts, in detail, a modification of this device, and

FIGURE 5 is a view of section VV taken on FIG. 1.

In FIGURE 1 the reference numeral 2 indicates an exhaust valve of aninjection combustion engine of known form. This valve is arranged withina valve housing 1 and is pressed upwardly against its seat 4 under theinfluence of a closure spring 3. A push rod 5, adapted to be moved upand down by an operating means (not shown), engages a double armedrocker 6 which is fulcrumed at 6:: in the housing 1, thereby effectingand controlling the opening and closing of the valve. Thus, when thepush rod 5 moves upwards the valve 2 is opened, whilst the latter closesunder the influence of its spring 3, in response to the descent of pushrod 5.

To facilitate hand cranking of the engine during starting, the valve isprevented from complete closure by means of a decompression device bymeans of which the development of a compression in the operating chamberof the engine to such an extent that it will make the cranking undulydifiicult is also prevented. In the illustrated example, thedecompression device consists of a rotatable decompression spindle 7which is mounted beneath the rocker 6 and extends at right anglesthereto. This spindle 7 has a tapered end which projects from the valvehousing 1 and is furnished with a setting lever 7a. The said spindle,moreover, is flattened by a milled-out portion 7b below the rocker 6.Thus, the portion of the rotatable spindle which is flattened at oneside thereof is in the nature of, and will be regarded as, a cam.Mounted in the lever 6, directly above this milled-out portion, is a setscrew 6b which constitutes a decompression abutment. If thedecompression spindle 7 is so turned and set by lever 7a that themilled-out portion 7b is located beneath the set screw 6b (FIGURE 1),the rocker 6 can move without obstruction in the counter clockwisedirection to permit of complete closure of the valve 2. As will beapparent from FIGURE 1, the internal combustion engine operates on aconventional 4-stroke cycle, viz. (1) suction, (2) compression, (3)expansion and (4) exhaust. Thus, in FIG- URE 1 the piston 12 is shown infull lines at its upper dead central position, i.e. the position ittakes up at the commencement of a suction stroke or at the end of acompression stroke. The open position of the exhaust valve 2 which itassumes during the exhaust stroke of the piston is indicated in chainlines. During each such exhaust stroke, combustion products escape fromthe cylinder 12a into the exhaust conduit 20, i.e. in the directionindicated by the chain line arrows. If, on the other hand, thedecompression spindle 7 is turned so that a cylindrical part of itsperiphery is opposed to the set screw 6b (FIG- URE 2 or FIGURE 3), thesaid screw will then strike the spindle 7 during a movement of therocker 6 in a counter clockwise direction so that the valve 2 cannotentirely close. FIGURE 2 illustrates the positions of the parts duringstarting of the engine. As will be seen, the exhaust valve 2 isprevented from closing entirely, so that during a compression stroke ofthe piston 12 the fuel-air mixture escapes, past the partially openexhaust valve and in the direction indicated by the full line arrows,into the exhaust conduit 2a. Consequently, there is no compression onstarting.

If an operator has brought this decompression device into its operativeposition to prevent complete closure of the valve 2 prior to thestarting of the engine, the device must be rendered inoperative again topermit the valve to close as soon as the fly wheel has achieved therotational rate required for starting. For this purpose the operator hasheretofore had to return the setting lever 7a by hand to the conditionillustrated in FIGURE 1. This manual movement is, however, verytroublesome in the case of large engines because, having regard to the 3internal friction in the engine, particularly under cold conditions, thecranking handle has to be turned with both hands.

To avoid this troublesome manual re-setting of the lever 7a afterstarting, which is also a frequent cause of accidents, We also providein accordance with the present invention, an automatic cut-out devicefor the decompression system. The construction of such cut-out deviceWill now be described. Secured on the decompression spindle 7 by a screw8a, alongside the milled-out portion 7b, is a driving disc 8. A collar ais provided on the push rod 5 and an annular bottom of a cup-shapedsleeve 9, functioning as a driver, is pressed down by a compressionspring 10 upon this collar. The upper end of this spring, whichsurrounds the push rod 5, bears against a spring ring 11 seated in agroove in the push rod. It is convenient to mention here that the piston12, which is reciprocable in the cylinder 12a, is coupled in theconventional manner to a connecting rod 13 which drives the crankshaft14. In turn, this crankshaft drives, through suitable gearing at 14a, acontrol cam 15 adapted to move up and down a mushroom-headed plunger 50.The purpose of the plunger 50 is to act on and move the push rod 5 inthe manner previously explained herein. For simplicity in FIGURE 1, theparts 5c, 13, 14, 14a and 15 are shown in purely diagrammatic fashion.

When the engine is running or is stopped, the decompression device is inthe inoperative condition illustrated in FIGURE 1. That is to say, theset screw 6b projects with play into the milled-out portion 7b, and anuntoothed portion of the disc 8 is disposed opposite to the rim 9a. ofthe sleeve 9. Thus, the valve 2 is completely closed and the sleeve 9moves idly up and down relatively to the stationary disc 8. But if, onthe other hand, a stopped engine is to be started with the help of thedecompression device and the latter is to be automatically cut-out againafter starting, the adjusting lever 7a is then first turned from theinoperative position illustrated in FIG- URE 1, in the clockwisedirection, until the rim 9a engages the driving teeth 8b on the disc 8.As a consequence of upward movement of the push rod 5 on cranking theengine, the disc 8 is turned through one toothed division in theclockwise direction (as viewed in the drawing), whilst the disc remainsstationary during the downward movement of the push rod 5. During suchdownward movement of the push rod the upper part of the sleeve 9,sliding idly over a tooth 8b is pushed away radially against the actionof the spring 10 so as to rock about the fulcrum 5a, being later broughtback into its axially parallel position under the spring action when therim 9a thereof drops behind the next tooth 8b. This procedure isrepeated until the rim 9a takes up a position behind the last tooth 8b,this coinciding with the relocation of the milled-out portion 7b beneaththe set screw 6b and the consequent termination of the decompression.

Thus, the duration of the decompression, that is to say the time duringwhich the valve is prevented from fully closing, is freely at thediscretion of the operator. If the operator sets the driving disc 8 insuch a way, before the commencement of the starting operation, that therim 9a --see FIGURE 2engages behind the first or second driving tooth 8bof the disc 8, the decompression period lasts longer; that is to say,the driving disc 8 will not be completely rotated and the decompressionwill not be terminated until after a number of strokes of the push rod5. On the other hand, the further the driving disc 8 is turned forwardin the clockwise direction relatively to the rim 9a, the shorter will bethe decompression period. It is to be clearly understood that even whenthere is provided an automatic cut out means for the decompression,which can be set to a chosen period, provision may nevertheless also bemade for a manual cut-out. For this purpose only the operative positionof the decompression spindle 7 has to be adjusted (see FIGURE 3), theset screw 6b bearing against the periphery of the spindle 7 andpreventing closure of the valve 2, whereas the rim 9a of the sleeve 9 isdisposed away from the toothed part of the driving disc 8. In this casea condition of so-called permanent decompression is set up and thislasts until the operator moves back the adjusting lever 7a by hand in acounter clockwise direction from the position shown in FIGURE 3 to thatshown in FIGURE 1. It is also to be noted that at least the primarypositions of the decompression device, for example the rest positionaccording to FIGURE 1 and the permanent decompression position of FIGURE3, can be determined by a sensitive catch mechanism, for example by aspring loaded ball catch associated with the decompression spindle.Moreover, if particular operating circumstances require it, a catchmeans, for example a pawl and ratchet arrangement, can additionally beused to permit rotary motion of the spindle 7 and of the disc 8 in theclockwise direction only. This will prevent the lever 7a and the disc 8from being accidentally moved in the counter clockwise direction duringthe setting operation, as a result of which the movement of the rim 9aof the driving sleeve 9 might be impaired by the teeth 819.

It is also pointed out that the restoring power of the spring 10, thewidth of the support collar 5m and the taper of the sleeve 9 should beso interrelated that the sleeve 9 cannot rock during the upward movementof the push rod 5 and will as a consequence positively entrain the disc8.

FIGURE 4 illustrates another constructional form of driving meansprovided on the push rod 5. Here again, these driving means take theform of a cup-shaped sleeve which surrounds the push rod 5 and is drawnup tightly against a collar 5b on the push rod by a nut 92 which isscrewed on to a screw threaded part 5a of the said push rod. Theperiphery of the sleeve 90 is slotted to a suitable depth at a number oflocations therearound so that the rim 90a of any one of the tonguesthereby formed is stiff enough to engage with the teeth on and turn thedriving disc 8 in response to upward movement of the push rod 5, whereasduring the downward stroke of the latter this tongue is able to bedeflected radially inwards against the spring influence so as to slideidly over the teeth 8b of disc 8. In this construction, as in thepreceding arrangement, the push rod 5 rotates unintentionally about itslongitudinal axis although this capability of rotation does not in anyway interfere with the proper functioning of the device. The reason whythe push rod 5 tends to rotate is that, in practice, the mushroom-headedplunger 50 is displaced to a small extent laterally in relation to thecam 15 and hence also to the longitudinal axis of the said push rod. Inother respects, this decompression device is operated in the same way asthe construction first described above.

The cost of constructing and installing the automatic cut out means in adecompression device according to this invention is very small. The saidmeans comprise only a small number of additional parts which can veryeasily be mass produced as turnings, stampings or pressings. Finally, itis to be additionally pointed out that the space taken up by the partsis very small and that therefore the cut out device can be installedWithout diificulties in any type of engine, and may even be readilyincorporated in an existing engine.

I claim:

1. In a valve controlled internal combustion engine, in combination, acylinder, a valve housing which adjoins said cylinder and has formedtherein an exhaust conduit, a valve seat at the entrance to saidconduit, an exhaust valve mounted within said housing, a closure springarranged normally to press said valve against said seat, a valve rockerfulcrumed in the valve housing and arranged for action upon the exhaustvalve to effect and control opening and closing thereof, a push rod foractuating the valve rocker, means for axially reciprocating said rod, adecompression cam which is arranged for action on the valve rockersuchwise as to hold the exhaust valve 01f its seat and so produce acondition of decompression, said cam being rotatable in a direction todiscontinue the decompression, a driving disc connected to said cam, anda driver which is provided on the axially reciprocable push rod, saiddriver consisting of a member of circular form in transversecross-section and having a peripheral edge which engages with and turnsthe driving disc in the aforementioned direction during valve openingstrokes of the push rod, at least a portion of the driver moving idlyaside radially in relation to the driving disc during valve closingstrokes of said push rod.

2. In a valve controlled internal combustion engine, in combination, acylinder, a valve housing which adjoins said cylinder and has formedtherein an exhaust conduit, a valve seat at the entrance to saidconduit, an exhaust valve mounted within said housing, means to urgesaid valve against said seat, a valve-actuating member, a push rod foroperating said member, means displacing said rod, a decompression camwhich, when operative, so influences the valve-actuating member as tohold the exhaust valve ofi its seat and so produce a condition ofdecompression, said cam being movable in a sense to discontinue thedecompression, a driving element associated with said cam, and a driverwhich is provided on the push rod, said driver being adapted to engageand move the driving element in the aforesaid sense during valve openingdisplacements of the push rod, at least a portion of the driver movingidly aside relatively to the driving element during valve closingdisplacements of said push rod.

3. In a valve controlled internal combustion engine, in combination, acylinder, a valve housing which adjoins said cylinder and has formedtherein an exhaust conduit, a valve seat at the entrance to saidconduit, an exhaust valve mounted within said housing, a closure springarranged normally to press said valve against said seat, a valve rockerfulcrumed in the valve housing and arranged for action upon the exhaustvalve to effect and control opening and closing thereof, a push rod foractuating the valve rocker, means for axially reciprocating said rod, adecompression cam which is arranged for action on the valve rockersuchwise as to hold the exhaust valve off its seat and so produce acondition of decompression, said cam being rotatable in a direction todiscontinue the decompression, a driving disc connected to said cam, acollar on the axially reciprocable push rod, an abutment on said rodspaced axially from said collar, a driver in the form of a cup-shapedsleeve of circular cross-section which surrounds the push rod and restson the collar, and a compression spring which surrounds the said rod andis interposed between the abutment and the bottom of the cup-shapedsleeve to resiliently bias the latter against the collar, the circularrim of the said sleeve being adapted to engage and turn the driving discin the direction to discontinue decompression during valve openingstrokes of the push rod and the sleeve moving idly aside radially inrelation to the driving disc during valve closing strokes of said pushrod.

4. A combination according to claim 3, wherein the cupshaped sleeve isdownwardly tapered and its circular rim is engageable with teeth on thedriving disc.

5. A combination accordingto claim 3, wherein the abutment on the pushrod is in the form of a ring seated in a groove in the said rod.

6. In a valve controlled internal combustion engine, in combination, acylinder, a valve housing which adjoins said cylinder and has formedtherein an exhaust conduit, a valve seat at the entrance to saidconduit, an exhaust valve mounted within said housing, a closure springarranged normally to press said valve against said seat, a valve rockerfulcrumed in the valve housing and arranged for action upon the exhaustvalve to effect and control opening and closing thereof, a push rod foractuating the valve rocker, this rod being rotatable about its axis,means for axially reciprocating said rod, a decompression cam which isarranged for action on the valve rocker suchwise as to hold the exhaustvalve off its seat and so produce a condition of decompression, said cambeing rotatable in a direction to discontinue the decompression, adriving disc connected to said cam, and a driver in the form of acup-shaped sleeve of circular cross-section which surrounds the push rodand is rigidly connected thereto, said sleeve being axially slitpartially along its length suchwise as to provide around its periphery aplurality of resilient tongues each capable of engaging and turning thedriving disc in the direction to discontinue decompression during valveopening strokes of the push rod and of being pressed idly aside radiallyin relation to the driving disc during valve closing strokes of saidpush rod.

' 7. A combination according to claim 6, wherein the cup-shaped sleeveis drawn up tightly against a collar on the push rod by means of a nutscrewed on to a screwthreaded part of the said rod.

8. In a valve controlled internal combustion engine, in combination, acylinder, a valve housing which adjoins said cylinder and has formedtherein an exhaust conduit, a valve seat at the entrance to saidconduit, an exhaust valve mounted within said housing, a closure springarranged normally to press said valve against said seat, a valve rockerfulcrumed in the valve housing and arranged for action upon the exhaustvalve to effect and control opening and closing thereof, a push rod foractuating the valve rocker, means for axially reciprocating said rod, adecompression cam in the form of a turnable spindle having a flattenedside, an abutment on the valve rocker for engagement with the peripheryof said spindle, the arrangement being such that with the spindle turnedto present the flattened side to the abutment the exhaust valve ispermitted to close fully to discontinue decompression whereas when thespindle is turned to present a normally rounded portion of its peripheryto the said abutment the said valve will be prevented from completeclosure to produce such a condition of decompression, a driving discrigidly connected to said spindle, and a driver which is provided on theaxially reciprocable push rod, said driver consisting of a member ofcircular form in transverse cross-section and having a peripheral edgewhich engages with and turns the driving disc in the aforementioneddirection during valve opening strokes of the push rod, at least aportion of the driver moving idly aside radially in relation to thedriving disc during valve closing strokes of said push rod.

9. A combination according to claim 8, wherein the spindle is furnishedwith a lever whereby said spindle can be initially set to determine thelength of the decompression period during starting of the engine.

10. In a valve controlled internal combustion engine, in combination, acylinder, a valve housing which adjoins said cylinder and has formedtherein an exhaust conduit, a valve seat at the entrance to saidconduit, an exhaust valve mounted within said housing, means to urgesaid valve against said seat, a valve-actuating member, a push rod foroperating said member, means displacing said rod, a decompression camwhich, when operative, so influences the valve-actuating member as tohold the exhaust valve off its seat and so produce a condition ofdecompression, said cam being movable in a sense to discontinue thedecompression, a driving element associated with said cam, a collar onthe displaceable push rod, an abutment on said rod spaced axially fromsaid collar, a driver in the form of a cup-shaped sleeve of circularcross-section which surrounds the push rod and rests on the collar, anda compression spring which surrounds the said rod and is interposedbetween the abutment and the bottom of the cup-shaped sleeve toresiliently bias the latter against the collar, the circular rim of thesaid sleeve being adapted to engage and move the driving element in theaforesaid sense during valve opening displacements of the push rod, atleast a portion of the driver moving idling aside relatively to thedriving element during valve closing displacements of said push rod.

11. In a valve controlled internal combustion engine, in combination, acylinder, a valve housing which adjoins said cylinder and has formedtherein an exhaust conduit, a valve seat at the entrance to saidconduit, an exhaust valve mounted Within said housing, means to urgesaid valve against said seat, a valve-actuating member, a push rod foroperating said member, means displacing said rod, a decompression camwhich when operative, so influences the valve-actuating member as tohold the exhaust valve off its seat and so produce a condition ofdecompression, said cam being movable in a sense to discontinue thedecompression, a driving element associated with said cam, and a driverin the form of a cup-shaped sleeve of circular cross-section whichsurrounds the push rod and is rigidly along its length suchwise as toprovide around its pcriphery a plurality of resilient tongues eachcapable of engaging and moving the driving element in the sense todiscontinue decompression during valve opening displacements of the pushrod and of being pressed idly aside radially in relation to the drivingelement during valve closing displacements of the push rod.

References Cited in the file of this patent UNITED STATES PATENTS1,805,578 Gardner et a1 May 19, 1931 FOREIGN PATENTS 451,428 GreatBritain Aug. 6, 1936 748,505 Germany Nov. 3, 1944 815,583 Germany Oct.4, 1951

